The present invention relates to a method and apparatus for treating tobacco, and, more particularly, to such a method and apparatus for applying a non-toxic tobacco beetle inhibitor to small leaf tobacco exemplified by oriental tobacco.
In tobacco processing, it is known to apply methoprene to the tobacco leaves as a larva growth inhibitor to eliminate the threat of beetle infestation in tobacco. Unlike conventional insecticides, (e.g., phostoxine, magnesium phosphide), which are highly toxic and have very short-term effects, methoprene is non-toxic, has a long lasting effect, and operates by interrupting the life cycle of cigarette beetles and other insects. Methoprene is commercially available in directly usable liquid form from Zoecon Corporation of Dallas, Tex. under the Registered Trademarks, "KABAT" and "DIANEX." Hereinafter, the term "liquid methoprene" will be used as a generic designation of these products of Zoecon Corporation and of other methoprene products in liquid form whether the product is a liquid phase, a liquid mixture, a liquid suspension or a liquid solution.
Liquid methoprene is applied on tobacco leaves during leaf processing using nozzles in a specified amount per unit volume of tobacco leaf to arrive at a spread of approximately 5 ppm of methoprene in the packed tobacco product. Therefore, it is important that the tobacco volume throughput per unit time is known at the point of application. In broad leaf tobacco production, liquid methoprene is applied after a redrying process, in which the redryer is preset to handle substantial volumes of tobacco per hour and with the leaves spread evenly over an apron conveyer. The latest liquid methoprene applying systems work with a weight slide connected to a solenoid cell which feeds information to a computer equipped to control a microflow pump. The computer calculates the tobacco throughout per minute and the microflow pump pumps a regulated amount of liquid methoprene through nozzles to be sprayed on the leaves.
However, in oriental tobacco leaf processing, redryers are not used and it is extremely difficult to measure throughput volume per unit time because of high fluctuation in volume throughout the processing system. The lay-out of traditional indigenous oriental tobacco processing factories makes it very expensive to use weight-belts, and measurements with photocells have been proven inaccurate because the high sand and dust content of oriental leaf tobacco distorts the light beams used with photocells.
Also, one of the main problems with the computer controlled system is that it is not adequately sensitive to measure small volume throughputs, which makes it of little or no use on smaller production lines typical of processing factories in the Mid-East. Another problem is the waste of liquid methoprene caused by a substantial turbulence in the open spraying cabin, resulting in an uncontrollable coverage of the tobacco leaf surface. Finally, the extremely dusty and sandy condition of oriental tobacco makes the process difficult to practice. The mechanism of the weight slide and solenoid cell system becomes clogged, and, because liquid methoprene is mixed with water at the end of the nozzles, a continuous buildup of mud around the nozzles occurs, and the mud eventually ends up in the product.
The computer controlled system is also expensive and, because of the high-tech design, it is difficult to calibrate and repair after a breakdown. All previously-mentioned problems with this form of application have also been reflected in laboratory analysis results, which show unsatisfactory coverage/spread of liquid methoprene in the finished product.
Oriental tobacco is characterized by its small leaf size, e.g., three to six inches in length. When stored for curing and later baled, the leaves agglomerate in "pads" which must be broken up or loosened into individual leaves for processing. Traditionally, mechanical leaf pad openers have been used to open the pads or to separate the leaves from each other. Such mechanical leaf pad openers use a beater, such as a revolving carousel of steel bars, to beat the pads physically until the leaves loosen up. These machines create an excessive amount of scrap because oriental leaf is not conditioned and tends to be very dry at the time of processing.
During the last few years, new developments in the processing of oriental tobacco have included the introduction of vibratory steaming tunnels. The tunnel solves the problems associated with mechanical leaf pad openers by using the kinetic energy in high-pressure, dry steam to condition the leaves and open the leaf pads, by development of extremely high turbulence in the closed environment of the tunnel. The system has been proven highly efficient in practice, and is gaining acceptance in factories which process oriental tobacco because of substantial reduction in scrap and the capability for obtaining a better end product with less leaf pads than previously possible.
One of the main requirements for the vibrating steam tunnel is an even flow of tobacco through the tunnel over steam nozzles. This is obtained by using a metering tube assisted with a volume backup system. Throughput volume is steady and the volume capacity of the tunnel is fixed according to the requirements of the processing system (e.g., 4 metric tons per hour).